Oriented electrical contactor



Sept. 11, 1928.

P. E. EDELMAN ORIENTED ELECTRICAL CONTACTOR Filed D60- 15, 1927FIG-3.6..

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Famed Sept. 11, 1928.

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Application Med December 15, 1927. Serial No. 240,215.

An object of my present invention is to increase the operating life ofthe oriented current conductin contactors.

A further ob ect is to improve the operating efliciency and obtain asteady flow of current thru the contact surfaces free from undesiredfluctuations.

A further object is to provide contact surfaces pre ared so as torequire no age treatment or orming for use.

A further object is to preparethe oriented current conducting contactors1n stabilized form with the materials contacting prepared physically ina molecular form whereby the atoms comprised in the materials arecombined in crystal form.

My invention is an mrprovement over rectifiers of the Pawlowski type anddiffers over prior art in the physical structure of the contactsurfaces. Heretofore it has not beenpossible to obtain dry contactrectifiers entirely free from current variations due to inequahties inreverse current flow caused by incomplete action at the contactsurfaces. 1

Since the initial discovery by F. Bran in 1874 that metallic sulphidesare capable of asymmetric conductivity various improvements have beenmade. Reasonably satisfactory rectifiers have been constructed for smallcurrent output where fluctuations are un mportant but all knownembodiments and 1mprovements of the prior art have'failed to provideproperly stabilized contact surfaces. Thus when rectifiers are madeaccording to the specifications of other patentces, such as S. Rubin, itis found that there 1s considerable reverse current flow thru thecontacts. This causes undesirable operating characteristic in that thisreverse current flow 1s not steady in value but changes transiently frommoment to moment as the contact surface breaks down and rebuilds itself.When such rectifiers are used in a radio POWEIdlIllt, the output tendsto be unsteady, varying from one to three tenths of a volt momentarily.When first connected in circuit, such rectifiers consume much current inthe reverse current flow and have a lower output, which builds up in afew minutes but does not reach'an entirely steady value. Examination ofthe discs of such rectifiers shows that only a part thereof has been inactive use and that the current has jumped from one spot to anotherwhenever a better path has been afforded during the transient physicalchanges in the contact surfaces.

I aim to overcome the transient variations pr ncipally by providing apermanently staihzed physical structure for the contactors at whichrectification of current flow is ac complished. By providing properphysical structure, reverse current flow is steadied because a constantcurrent path is provided at the junction of the contactors instead of atransiently variable path. Therefore the load on the feeding transformerfor the rectifier becomes constant as regards the current consumption inreverse current flow instead of variable as in prior rectifier elementsin which this reverse current flow is unsteady and draws more or lesscurrent from time to tune, which causes the voltage to rise and fallaccording to the changes in the load on the feeding transformer.

I illustrate, by way of example, a suitable embodiment of my inventionin the accompanying drawings in which Figure 1 is a diagram of arectifier circuit employing my oriented contactors; Figure 2 is asectioned front elevation of my oriented contactors embodied in arectifier structure; Figure 3 is a sectioned front elevation of thecombined metallic sulphide and metal structure I employ in my contactdisc; Figure 4 is a front elevation of the crystalline alloyed physicalsurface combined on the positive contact disc of my rectifier; Figure 5is a sectioned view showing the preparation of the negative contactdiscs; and Figure 6 is a diagram showing the preparation of thecrystallized metal positive contact discs.

Various changes and modifications may be made without departing from thespirit of this invention and within the scope of the appended claims. I

Referring now to Figure 1, a transformer 1 supplies current to a fullwave rectifier 2 which consists of oriented contactors 14, 15; 16, 17;18, 11; and 12, 13 arranged like a double pole double throw switchconnection as is customary in this art. The output terminals are,positive terminal 8, and negative terminal 9.

Each particular pair of contactors as for example 14, 15 'are comprisedby an electronegative compound surface 14 combined with an electrode 7,with 14 pressing against an cleotronegative crystallized metallicsurface 15 alloyed on positive electrode 3. The other contactors andelectrodes are similarly arranged in pairs and interconnected in correctpolarity as designated by numerals 19, 16, 17, 6; 21, 18, 11, 20; and 4,12, 13, 5; it being understood that additional contactors may beemployed in series or parallel connection as is customary in this art.

For a particular instant current can flow from transformer 1 to a loadcircuit connected at terminals 8 and 9 via 3, 15, 14, 7; and 21, 18, 11,20, assuming that no reverse current can flow. However such is not thecase and there is at the same instant a possible circuit from thetransformer .1 via either the pathway 20, 11, 18, 21; 6, 17, 19, 16 orthe pathway via 4, 12, 13, 5; wire 10, and 7, 14, 15, 3. The amount ofcurrent leaking thru such reverse current pathways depends on variousfactors and I aim principally to maintain same at "uniform instead oftransiently fluctuating values. Suppose for a particular time instantthat load current is flowing as stated and that leak current is alsoflowing as indicated. Then if the leak current should increasetransiently the transformer 1 must not only supply the load current andthe normal leak current, but also the increase in leak current. Suchincrease on the transformer output terminals 22 causes the voltage atsuch terminals to drop with resulting fluctuation at output terminals 8.and 9. A similar action occurs at each reversal of polarity intransformer 1 during each cycle and thru the particular contacts ofrecti er 2 concerned, also in the particular leakage pathways concernedfor each instant. From such considerations it appears that since leakagecurrent cannot be entirely avoided, my conception of providing steadyvalues for the leakage current instead of transiently varying valuesprovides a practical solution of the difficulty. This is accomplished byproviding a correct physical structure for the oriented current carryingcontactors so that the leakage current path is uniform and is attainedas herein set forth.

It is manifest that uniform flow of reverse current as distinguishedfrom load current thru rectifier 2 cannot be had with any phys icalstructure for the oriented contact elements which requires continualbreaking down and building up to maintain the oriented contactors inoperative relation. Thus in Pawlowski, U. S. Patent No. 830,924, Sept.11, 1906, typical of one type of physical structure for the contacts,the oriented action requires a transfer of electrons from the positiveelement and negative element under the influence of the current flowwhich sets up suflicient heat to cause minute sparking acwhich companiedby a continual change in chemical or electrochemical recombination ofthe elements at the contact surface. This condition is unstable andwhile suitable for battery charging purposes, gives rise to fluctuationsin the output potential when used in a true battery eliminator filtercircuit device. Similarly, the other type of contact structure of the U.S. patents to Rubin Nos. 1,649,- 742 and 1,649,743 or 1,649,744 ofNovember 15, 1927, are typical, attem t to improve on Pawlowski, cited,by suppiying a prepared non-crystalline surface on the positiveelectrode. However, it is established that rectification or currentorientation only occurs at a true crystalline junction and such lattertype of contactors depend for their action on a subsequent partialbuilding up and breakin down of a crystalline junction surface, whicalso depends on current flowing to cause sufficient thermal and chemicalor electrochemical action to set up an acting physical crystallineoriented junction between the positive and negative contactors. Suchlatter type is also found to vary in output, as may be expected fromconsideration of this action and while the action may be stabilized toan extent by an aging process the reverse flowing current is likely tochange in amount at any particular time depending on the condition ofthe crystalline structure at the contact j unction at any instant.However by providing a permanent crystalline structure at the contactsurfaces in accordance with my invention, the need for the said breakingdown and rebuild ing of the crystalline nature of the contact junction,necessary for real oriented contacts, is avoided and while there will besome leakage current it will have a steady pathwa afforded therefor viasaid permanent crysta line contact surface and not need to rebuild newpathways along the electrode surface from time to time. Thus, whereas inthe prior art only a temporary and partial crystalline structure hasbeen indirectly attained at the active junction of the orientedcontacts, I provide a permanent prepared crystalline active junctionover the entire contacting surface of the contacts and on both thepositive and negative contacting elements.

Supporting evidence for this essential theory of contact surfaces willbe found in the book Principles of Wireless Telegraphy by G. W. Pierce,McGraw Hill Pub. Co., Wireless Telegraphists Pocket Book by J. A.Fleming, the \Vireless Press Ltd. London 1915; L. W. Austin, Bulletin ofBureau of Standards No. 94, Vol. V, 1908, Washington, D. (3.; W. D.Eccles, Proceedings Physical Society of London Vol. XXV 1913, as well asin the Pawlowski patent hereinbefore mentioned.

Referring to Figure 2, a suitable series assembly of pairs of orientedcontactors for a half wave rectifier element is shown. A

bolt 25 carries an insulating sleeve 23 and a yielding insulating washer24. Negative contact electrodes 35, 31; 34, 30; and 33, 29

are alternately disposed on sleeve 23 betweenpositive contact electrodes41, 38; 40, 37 and 39, 32 which are also carried on sleeve 23. Athermically expansible washer 26 causes the positive and negativecontactors aforesaid to press together when nut 27 is tightened permanently on bolt 25. Washer 26 may be made from an alloy containingantimony and tends to equalize the pressure at extremes of temperaturedue to its property of expansion. The yielding washer 24 cooperates tomaintain approximately uniform pressure on the said electrode contacts.The operating terminals of the rectifier shown in Figure 2 are thepositive metal electrode 32, and the negative metal electrode 31. Allnegative electrode elements, as for example 35, 31 are constructedsimilarly; and all positive elements, as 41, 38 are similarlyconstructed alike. The negative electrode or disc is shown-separately inFigure 3, and the positive electrode unit is shown separately in Figure4.

In Figure 3, a copper washer 44 has a terminal 28 formed therewith.\Vasher '44 can be of any suitable electronegative metal, and copper issuitable. The washer 44 is thermochemicall coated with anelectronegative compoun of the metallic material of washer 44combinedwith a non-metallic element; a suitable composition for thiscoating 43 being either copper sulphide CuS or Cu S. Or a selenide ofcopper is also suitable. It is also permissible to intermix somemetallic or powdered copperin the crystal mass 43. The terminal portion28 of washer 44 is required only on units as shown in Figure 3 which areto serve asterminals to an external circuit and may be omitted on otherdiscs like 44 to which no external circuit is directly connected. Aconvenient manner in which to apply terminal 28 is to scrape awaysufficient of the material 43 to permit soldering or welding strip 28 tometal washer 44.

A suitable manner for preparing elements as in Figure 3 is indicated inFigure 5. The orifice 42 of washer 44 is also coated with material 43 bythis method, but the washer 44 is notentirely chemically converted toform the material 43, its inner base 44 remaining true metallic copper.Thismetallic core 44 assists in heat conduction from the electrodecoating 43 of Figure 3 as well as giving it mechanical strength toprevent cracking of the brittle crystalline homogeneous coating mass 43.

A crucible 45 is shown in Figure 5 heated by a gas flame 49. A fire claycover 46 is luted on crucible 45 by cement 47 to prevent air leakagetherein. A layer of flowers of sulphur 48 is spread in the bottom ofcrucible 45. Over sulphur 48, which should be of are grade, a refractorylayer 50 is placed. hlS

lytically refined copper in soft or semi-hard sheet stock about to 3- 2"thick. These washers 51 are stacked, out of contact with each other incrucible 45, with the refractory material 50 spread thereon andtherebetween. The refractory material 50 appears to have beneficialproperty of distributing the thermo-chemical reaction evenly. The cover46 is first secured over crucible 45 and then heat is applied fromsource 49 for a short time to melt the sulphur 48 and vaporize it. Thesulphur vapor thus produced spreads thru the interior of crucible 45 andreacts with the copper metal pieces 51.

The amount of deposit on washers 51 can be controlled by regulating thetemperature and time of treatment. Thereafter the crucible is cooled,the contents removed, and the coated washers 51 are cleaned andpolished. The treatment should not be allowed to convert all of thecopper in the washer, it being desirable to retain the inner portion ofwasher 51 unattacked by the sulphur so as to reinforce the finishedcontact element, as the sulphide coating itself is brittle. Emery orother abrasive material is suitable for polishing the discs 51.

The washers retain their original fiat form by this treatment and do notbuckle out of shape. As an example, a small crucible can be heated foras brief a time as five minutes small portion of zinc or tin beforeapplying the treatment in crucible 5. Or the copper on washers 51 whichis to be converted to copper sulphide may first be plated to a suitablethickness by electroplating said copper on a soft steel washer base. Thecoating obtained has a bluish black color but other colorings can beobtained by varying the proportions and time of treatment ranging fromgreenish black color to a deep blue corresponding to differentproportions of combination. The bluish-black colored material issuitable for use and is principally crystalline copper sulphide CuS withpossibly some 011 s also present. The crystalline structure in the massis evident and is uniformly obtained by this treatment. 7

The positive contact element indicated by Figure 4 preferably comprisesa sheet magnesium washer 53 having a terminal portion 52 formedtherewith and an orifice 54. The crystalline coating is applied byplating a deposit of magnesium metal thereon to combine as an alloy withwasher 53, the coating 55 being physlcally converted to crystalline formintimately adherent to disc 53. Disc 53 can be some other metal thanmagnesium, if properly cleaned before coating 55 is applied thereto.

A suitable treatment to produce positive electrodes, as in Figure 4, isindicated n Figure 6. A roll of sheet magnesium 56 is fed over and undera series of rollers 63. In passing thru tank 57 the magnesium is firstcleaned by a cleaning fluid 60 comprising diluted hydrofluoric acid,then washed in tank 71 with hot water continuously replaced by freshwater. In passing thru tank 58 the magnesium sheet is electroplated withan electro-alloyed deposit of magnesium. Tank 58 contains a suitableelectrolyte including a salt of magnesium such as magneslummonophosphate, magnesium chloride or magnesium nitrate acidified, as iscustomary in the plating art; and electrode 73 of metallic magnesiumconnects with battery to feed the plating current to the sheet magnesium75 by brush contact 64. A washing tank 74 permits the sheet magnesium topass to container 59 where a blast of warm air is supplied via pipe 76to dry the sheet 75 and rubbing electrodes 66 insulatively mounted onsupport 59 serve to transfer alternating current to sheet 75 fromtransformer 68. Transformer 68 feeds alternating current to sheet 75 bymeans of brush contact 77 and rubbing contactors 66. The sheet 75 isthen cut by shears 69 and stamped into washers by die 70 to formcompleted contact elements 72.

Magnesium resembles zinc in its property of crystallizing whenelectro-galvanized onto a metallic surface. The size of the crystals canbe regulated by controlling the treatment and regulatin the currentdensity. The potential applied by transformer 68 should also beproportioned to obtain the smaller sized crystals, as can be determinedby experiment according to the rate at which roll 56 is used. Bysuitable care and precautions in keeping sheet aluminum clean, aluminumsheet can be plated and prepared with crystallized magnesium coating insimilar manner.

The prepared positive contact elements should be promptly assembledimmediately after production thereof as the crystalline magnesiumcoating is likely to collect a coatin of oxide if left standing for aperiod before assembling same for use. Crystalline magnesium will berecognized by its bright crystalline appearance, whereas magnesium whichhas collected oxygen from the air will have a dull appearance.

I have now set forth fully my conception and described suitable meansfor attaining the objects set forth. This invention conproduct, whichmay be prepared as any other suitable process or cerns the specified orby method.

I claim;

1. A rectifying device consisting of a pair of oriented electricalcontactors comprising an electropositive metallic electrode having acrystallized metallic surface alloyed thereon, and an electfonegativemetallic electrode having a chemically combined electronegative compoundof a nonmetallic electronegative element coated thereon, the contactjunction being located between said crystallized metallic surface andsaid non-metallic coated element.

2. A rectifying device consisting of oriented electrical contactorscomprising a crystallized metal surface plated on a positive electrodeand an electronegative compound of a non-metallic element chemicallycombined with a supporting negative electrode, and means to press saidcrystallized metal surface against said electronegative compound.

3. A rectifying device oriented electrical contactors consisting ofcrystallized magnesium metal alloyed on the surface of a positiveelectrode. and a cooperating metallic sulphide contacting therewith andchemically combined with a negative me tallic electrode.

4. A rectifying device consisting of oriented electrical contactorsconsisting of a positive contact'element comprised by a metal electrodeon which crystalline metallic magnesium is electro-alloyed. and anegative contact element touching said crystalline metall1c magnesium ofsaid positive contact, said negatlve element contacting only with saidcrystalline magnesium and not directly with the supporting metalelectrode therefor.

5. A rectifying device consisting of oriented electrical contactors, oneof which consists of a metal electrode having a crystallized metallicmagnesium surface thereon. and a cooperative negative electrode pressedthereon and consisting of a sulphide of copper combined chemically withmetallic copper.

6. A rectifying device consisting of electrical contactors consisting ofpositive and negative electrodes pressed together, said posltiveelectrode comprising a crystallized metallic magnesium surface carriedon a metal disc, and said negative electrode comprising a homogeneouscrystalline mass of a sulphide of copper chemically combined on ametallic copper disc.

7. A rectifying device consisting of electrical contactors consisting ofpositive and negative electrodes, a crystalline surface of metallicmagnesium alloyed on said positive electrode. and a crystalline mass ofa compound of copper chemically combined with an electronegativenon-metallic element therconsisting of homogeneous interlocked mass ofcopper sulphide thermo-chemically formed thereon, the terminals for saidelectrical contactors being firstly the positive electrode, and secondlythe said electronegative metal.

In Witness whereof I have hereunto set my 5 hand this 12th, day ofDecember, 1927.

PHILIP E. EDELMAN.

